Sarah Jessica Parker has opened up about stepping in for Demi Moore in the upcoming biopic "Lovelace."

The "Sex and the City" star was asked to fill in when Moore was forced to cancel her appearance in the film as Gloria Steinem.

"It was difficult because, obviously, the circumstances are not ideal," SJP told Access Hollywood at the amfAR New York Gala on Wednesday.

"I obviously conveyed that to the filmmakers [and] that I was aware and I was sorry for the reasons that they had to reach out to me," continued the actress. "Also, of course, the somewhat daunting task of playing somebody with very little time [to prepare], who was obviously such an important person in the women's movement, but also played such a pivotal role in Linda's life."

The 46-year-old actress added, "And to do it well and properly and not an impersonation, but rather a complete person with not a lot of screen time and not a lot of preparation."

"Lovelace" stars Amanda Seyfried who will play Linda Lovelace, a woman who was abused and forced into the pornography industry by her husband before taking control of her life.

Filmmakers Rob Epstein and Jeffrey Friedman confirmed SJP's fill-in last month as production for the film had just began.

Also starring in the movie are actors Hank Azaria, James Franco, Sharon Stone, and Juno Temple, among others.

Moore pulled out of the film after weeks of a public struggle to cope with rumors of Ashton Kutcher's infidelity as well as her divorce from the actor. The 49-year-old is seeking treatment for "exhaustion" at an undisclosed location.

Her rep added that Moore needs professional assistance "because of the stresses in her life right now," reported TMZ.

"Lovelace" will be released later this year with the date yet to be announced.